1. Field of the Invention
The present invention relates to an internal combustion engine including a balancer shaft rotated in synchronization with a crankshaft, and particularly to an apparatus for feeding lubricating oil to the crankshaft and the balancer shaft of the internal combustion engine. In addition, the present invention relates to an oil feeding mechanism for a starter driven gear bearing, wherein a starter driven gear is disposed on a crankshaft of an internal combustion engine.
2. Description of Background Art
To suppress the vibration of an engine, a balancer shaft having an eccentric weight has been disposed in parallel to a crankshaft and rotated in synchronization with the balancer shaft.
The lubrication for each bearing of the balancer shaft has been made as follows. An accessary part such as an orifice, jet, or control bolt composed of a bolt for mounting a pipe which is perforated, is provided in an oil passage branched from a lubricating oil main gallery communicated to an lubricating pump. The oil feeding for each bearing is made by way of the above part, and further the amount of oil fed to each bearing is adjusted by the part.
In an internal combustion engine disclosed in Unexamined Japanese Patent Publication No. HEI 2-211327, a central oil passage and side oil passage are provided under a crankshaft and a balancer shaft so as to be parallel to these shafts, and these oil passages are communicated to each other by way of a communication oil passage. Oil passages are provided between the central oil passage and each bearing of the crankshaft, and between the side oil passage and each bearing of the balancer shaft. One of these oil passages is connected to a lubricating oil pump.
The above-described lubricating oil feeding apparatus using the orifice or the like is disadvantageous in that the lubricating oil passage is complicated and thereby the number of parts is increased. Also screwing and assembling are required for inserting the orifice or the like and thereby the number of processing steps is increased. Another disadvantage lies in that since the flow of the lubricating oil is restricted by the orifice or the like before reaching the oil hole of the bearing, it takes a lot of time for the lubricating oil to reach the interior of the bearing after starting of the engine.
In the lubricating oil feeding apparatus disclosed in Unexamined Japanese Patent Publication No. HEI 2-211327, the construction of the oil passage is relatively simple, and the number of parts is small; however, it is difficult to suitably adjust the amount of oil fed to each bearing. Namely, to effectively utilize the lubricating oil, it is required that the amount of oil fed to each bearing of the balancer shaft to which a relatively small load is applied is made smaller than the amount of oil fed to each bearing of the crankshaft to which a large load is applied. The above lubricating oil feeding apparatus, however, cannot meet such a requirement.
There has been known an internal combustion engine mounted on a motorcycle of a type in which, as shown in FIGS. 14 and 15, a rotor 104 of a power generator 103 is integrally mounted at the leading edge of a crankshaft 102 projecting sideward from a crankcase 101, and a starter system 105 is disposed between the rotor 104 and the crankcase 101.
In this starter system 105, a starter driven gear 106, which is rotated in the starting direction by way of a starter motor and an intermediate gear (not shown), is adapted to transmit the starting torque to the rotor 104 and the crankshaft 102 by way of a one-way clutch 107. In operation of an internal combustion engine, the starter driven gear 106 is stopped along with the stoppage of the starter motor, and thereby the starter driven gear 106 is rotated relative to the crankshaft 102. Accordingly, a bearing is required to be provided between the crankshaft 102 and the starter driven gear 106. The above bearing cannot have a structure of forcibly supplying lubricating oil as in a slide bearing 109 of the crankshaft 102, and it is constituted of a needle bearing 110.
In the needle bearing 110 of the starter one-way clutch 107 shown in FIG. 14, an inner race 111 is used. On the contrary, as shown in FIG. 15, the inner race 111 is replaced by a starter driven gear bearing portion 102a of the crankshaft 102 which is subjected to high frequency quenching. The latter is disadvantageous in increasing the number of the processing steps, resulting in increased cost.